二极管箝位型五电平变换器中点电位控制研究

Neutral-point Voltage Balancing Research for the Five-level Converter

针对二极管箝位型五电平变换器中点电位受负载功率因数、调制度以及不同类型空间矢量等多种因素影响而存在的不平衡问题,首先对影响直流侧电容平衡的各类因素进行了理论分析,接着基于虚拟空间矢量设计中点电位平衡控制方法,以实现不同运行工况下的中点电位平衡。考虑直流侧均压电容的累积偏移效应,对虚拟矢量分配进行占空比修正。最后,Matlab数字仿真和样机平台验证了所研究中点电位控制方案有效性。

The neutral-point voltage usually becomes unbalanced for the diode clamped five-level converter for a variety of reasons,such as load power factor,modulation and the effects of the different types of space vectors.A novel neutral-point voltage balancing strategy using the virtual voltage vectors has been studied based on the theoretical analysis of the controllable area of the direct current link capacitance voltage.Furthermore,a duty correction for the virtual vectors also has been given for the consideration of cumulative offset of the capacitors.Numerical simulations and experiments have been carried out the make verification of the proposed neutral-point voltage balancing strategy.